public void CopyShippingAddressToBillingAddress()
 {
     _billingAddress = _shippingAddress?.CopyOf();
 }
 public void SetBillingAddress(PostalAddress billing)
 {
     _billingAddress = billing;
 }
 public void SetShippingAddress(PostalAddress shipping)
 {
     _shippingAddress = shipping;
 }